7012

• UCREFRP Catalog Number: 7012
• Author: Cross, J. N.
• Title: Ecological Distribution of the Fishes of the Virgin River ‎(Utah, Arizona, Nevada)‎.
• USFW Year: 1975.
• USFW - Doc Type: University of Nevada,
• Copyright Material: NO

1.
INTRODUCTION
The Virgin River heads in southwestern Utah at the southern edge
of the Markagunt Plateau. It flows. generally southvresterly across the
western boundary of the Colorado Plateau into the Basin and Range
Province where it turns southerly and flows into lake riead. Prior to
the construction of Hoover Dam (1935) the hioapa River vras a tributary
~to the Virgin River which emptied directly into the Colorado River.
Since the completion of the dam and the filling of Lake Plead, the
Moapa and Virgin Rivers flow separately into the Overton Arm of
the lake. The~Virgin River is approximately 320 km long and traverses
three states (Utah, Arizona, Nevada) along its course.
The river is characterized by widely variable discharges and high
sediment loads typical of desert streams. The fish fauna is
depauperate; Woodbury (1933, p.~184) referred to the Virgin River as
". an aquatic desert because of its paucity of life forms" which he
attributed to the periodic floods that scour the river bottom. The
native fishes of the Virgin River are uniquely adapted to this
fluctuating environment as is evidenced by the degree of endimism:
two (Lepidomeda m. mattispinis and Gila robusta seminuda) of tl~e six
native species are endemic subspecies; a third species (Plagopterus
argentissimus), once present in the Gila River system, is now restricted
to the Virgin River; two (Catostomus Zatipinnis and Pantosteus cZaxki)
of the remaining species are only found in the Colorado River basin;
the last native species (Rhinichthys oscuZus) is ubiquitous west of
the Rocky Mountains.